You may be hitting the memory limits on your development machine as VS is 32-bit.

I don't use SSDT or RS 2012 so can't confirm it happens there but I used to get this a lot using BIDS/SQL 2008.

My solution then was to deploy to the Report Server web site & run from there.

You can put it in a hidden folder or restrict access to just yourself if you don't want others to run it just yet.